Performance criteria-aspects of scheduling , Mechanical Engineering

Performance Criteria

This is assumed that an FMS is the part of a superior production process. Consequently the performance of the FMS is not a major goal but imply to attain cost-efficient timely production in the whole system. In hierarchical decentralized systems, the recent state of technology, complex production systems should be controlled. The decisions in the subsystems should be based upon local due dates and local earliest possible beginning times that are offered via the higher-level scheduling system. For a smooth operation of the whole system, a narrow distribution of the deviations from planned process is necessary.

Thus, the usual performance criterion is considered as minimal tardiness. Earliness is neither honored nor punished, since in a complex system the advantages of local earliness are doubtful. The tardiness of all jobs that are ended on time or earlier is zero. Throughput time or machine consumption are not utilized as criteria, since on the long run (we utilize extremely long horizons for the evaluation) the task of a production system is to generate the goods to be delivered on the right time where the demanded throughput times may vary extremely among the jobs; hence, the average throughput time might be a misleading indicator. Obviously, tardiness must all time be looks relative to a specific demanded flow factor distribution, indicated via the time pressure level in the present case.

There are a number of various reasonable measures of tardiness. This is identified that these dissimilar measures in usual cannot be minimized concurrently. In cases of high loads of the system, algorithms which prefer shorter operations offer good values of average tardiness Tmean but at the expense of a minute fraction of the jobs that suffer from extremely large delays. If an FMS is integrated in a superior overall production process, not only a minute value of Tmean is desired but also a narrow distribution of the delays approximately this value, since larger discrepancies among planned and attained completion times create problems for the another local schedule. Thus, the subsequent three criteria are utilized:

Average overall tardiness (over all jobs)

 

 

 

                           581_Performance Criteria-aspects of scheduling.png

Notice that Tmean  is not subtracted in the definition of Trms, consequently Trms  is not a variance but a measure of concerns tardiness and the dissimilarity of Tmean  and Trms  implies the width of the distribution. The associate emphasis is specified to any of the three criteria depends upon the exact situation. Generally, Trms will be the most suitable single criterion.

Posted Date: 3/5/2013 7:25:19 AM | Location : United States







Related Discussions:- Performance criteria-aspects of scheduling , Assignment Help, Ask Question on Performance criteria-aspects of scheduling , Get Answer, Expert's Help, Performance criteria-aspects of scheduling Discussions

Write discussion on Performance criteria-aspects of scheduling
Your posts are moderated
Related Questions
how to prove that heat and work is path function?

Calculate the vertical deflection: Calculate the vertical deflection at the tip of the cantilever shown in Figure Figure Solution Measuring the distance x f

Estimate the Machining Time A hollow workpiece of 60 mm outside diameter and 150 mm length is held on a mandrel among centers and turned all over in 4 passes. If the approach

Q. Insulation on Flanges and Valves? Valves, flanges, and unions shall not normally be insulated unless specified by OWNER. All other fittings are to be insulated. Fittings

Main characteristics of couple: Sol.: The main characteristics of couple 1. The algebraic sum of the forces, having the couple, is zero. 2. The algebraic sum of moment

Explain Milling Fixture? A milling fixture is a work holding device which is firmly clamped to the table of milling machine. It holds the work piece in correct position as

(a) Illustrate First Law of Thermodynamics for a Closed System undergoing a change of state and show that ‘Energy' is a property of the system. (b) A cylinder contains 1 m 3 of

Q. Principal design criterion of Plant layout? Safety-in-Design is a key factor associated with the layout design of any facility. The principal design criterion is to minimize

Determine the horizontal component of the force: A force of 80 N is working on a bolt as illustrated in Figure. Determine the horizontal and vertical components of the force.

Calculate pressure on each side of spherical ball : Heavy spherical ball of weight W rests in V shaped trough whose sides are inclined at the angles and to the horizontal